The present invention relates to an image encoding device and to technology which is effective when applied to a moving image recording and reproducing device at large, for example, a digital camera which possesses hardware and software for moving image encoding/decoding, a digital video camera, a DVD (Digital Versatile Disc)/HDD (Hard Disc Drive) recorder, a mobile-phone, and the like.
In the system treating a moving image code, HD (High-Definition) has entered the proliferation period, and utilization of a larger screen such as 4k digital cinema, a super Hi-Vision, etc. is advancing on the research level. An image encoding device and an image decoding device handling these signals are required to possess a high processing capability. In order to improve a processing capability with a low power consumption (at a low operating frequency), the parallel encoding is proposed, which will become indispensable technology when processing a moving image in the future. The H.264 standard can provide a high compression up to 1/100- 1/200, maintaining a high-quality image. Therefore, the H.264 standard is employed as a coding standard of terrestrial digital broadcasting and the next generation DVD standard, and also planned to be adopted as a coding standard of the future 4k digital cinema or super Hi-Vision.
The following documents treat the moving image parallel encoding technology and the encoding technology with a quantization parameter changing in units of macroblock.
Patent Document 1 (Japanese patent laid-open No. 2008-42571) discloses technology in which a screen of a moving picture is divided into plural areas, and encoding is performed in parallel, in order to encode a large screen moving picture. Patent Document 2 (Japanese patent laid-open No. 2000-333180) discloses a method in which, based on the reason that a first and a last macroblock of each slice of an image processing area should not be a skip macroblock, the macroblock type of the skip macroblock concerned is changed. Non-patent Document 1 (“Test Model 5”, MPEG.ORG, online, searched on Mar. 24, 2008, the Internet <URL:http://www.mpeg.org/MPEG/MSSG/tm5/>) discloses technology in which a quantization parameter is changed in units of macroblock in order to adjust the rate. Non-Document 2 (Tomokazu Murakami and Isao Karube; “A consideration on setting up a quantization parameter of the macroblock level in H.264/AVC”, PCSJ2004, November 2004) discloses technology in which a quantization parameter is changed in units of macroblock depending on an image to attain a high-quality image.